U.S. patent number 7,791,252 [Application Number 11/668,656] was granted by the patent office on 2010-09-07 for ultrasound probe assembly and method of fabrication.
This patent grant is currently assigned to General Electric Company. Invention is credited to Charles Edward Baumgartner, David Chartrand, Kevin Matthew Durocher, Robert Stephen Lewandowski.
United States Patent |
7,791,252 |
Baumgartner , et
al. |
September 7, 2010 |
**Please see images for:
( Certificate of Correction ) ** |
Ultrasound probe assembly and method of fabrication
Abstract
An ultrasonic imaging system wherein an exemplary system
includes an array of transducer elements arranged along a first
plane for transmitting first signals and receiving reflected
signals for image processing. Circuit structures each have a major
surface positioned in a co-planar orientation with respect to a
major surface of another of the circuit structures to provide a
sequence of the structures in a stack-like formation. Electrical
connections are formed between adjacent circuit structures in the
sequence. A connector region on each circuit structure includes a
distal portion extending away from the major surface-with distal
portions of connector regions of adjacent structures spaced apart
from one another. A first wiring pattern extends from the major
surface to the distal portion of the connector region. The
plurality of circuit structures are configured to provide a second
wiring pattern including at least some of the electrical
connections formed between the circuit structures, extending from
one or more of the first wiring patterns to multiple of the
transducer elements.
Inventors: |
Baumgartner; Charles Edward
(Schenectady, NY), Lewandowski; Robert Stephen (Amsterdam,
NY), Durocher; Kevin Matthew (Waterford, NY), Chartrand;
David (Mesa, AZ) |
Assignee: |
General Electric Company
(Niskayuna, NY)
|
Family
ID: |
39595539 |
Appl.
No.: |
11/668,656 |
Filed: |
January 30, 2007 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20080178677 A1 |
Jul 31, 2008 |
|
Current U.S.
Class: |
310/334; 367/157;
367/155; 73/606 |
Current CPC
Class: |
B06B
1/0629 (20130101); G03B 42/06 (20130101); A61B
8/00 (20130101); G01S 15/8925 (20130101) |
Current International
Class: |
H04R
17/00 (20060101) |
Field of
Search: |
;310/334 ;367/155,157
;73/606 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Benson; Walter
Assistant Examiner: Gordon; Bryan P
Attorney, Agent or Firm: Asmus; Scott J.
Claims
The invention claimed is:
1. An ultrasonic imaging system comprising: an array of transducer
elements arranged in rows and columns along a first plane for
transmitting first signals and receiving reflected signals for
image processing; and a plurality of circuit structures each having
(a) a major surface positioned in a co-planar orientation with
respect to a major surface of another of the circuit structures to
provide a sequence of the structures in a stack-like formation
wherein electrical connections are formed between adjacent circuit
structures in the sequence, and wherein the major surfaces are each
positioned along a plane substantially parallel with the first
plane, (b) a connector region having a distal portion extending
away from the major surface, with distal portions of connector
regions of adjacent structures spaced apart from one another, and
(c) a first wiring pattern extending from the major surface to the
distal portion of the connector region, the plurality of circuit
structures configured to provide a second wiring pattern, including
at least some of the electrical connections formed between the
circuit structures, extending from one or more of the first wiring
patterns to multiple of the transducer elements, wherein two or
more rows and/or two or more columns of said array are electrically
connected to at least one of said first wiring pattern and said
second wiring pattern.
2. The imaging system of claim 1 wherein each of the circuit
structures is a flexible circuit board, and major surfaces of
adjacent structures are bonded to one another, forming a relatively
rigid portion in the sequence relative to the spaced apart distal
portions.
3. The imaging system of claim 1 wherein the electrical connections
between two of the adjacent circuit structures include conductive
vias formed in each of the structures and contact pads formed along
surfaces of the two structures facing one another with pads on the
facing surfaces connected to one another thereby effecting
connection between vias formed in the different structures.
4. The ultrasonic imaging system of claim 1 wherein: each major
surface of a circuit structure is along a central portion of the
circuit structure and each circuit structure includes at least two
connector regions, each having a distal portion extending away from
the major surface, a first of the distal portions extending away
from the major surface along a first direction and a second of the
distal portions extending away from the major surface in a
direction different than the first direction, with distal portions
of adjacent connector regions extending away from the major surface
in the first direction spaced apart from one another and distal
portions of adjacent connector regions extending away from the
major surface in the second direction spaced apart from one
another.
5. The system of claim 4 wherein a first of the structures is
positioned closest to the array relative to a second of the
structures and is configured to: receive electrical signals from
transducer elements in all of the columns in the array; provide
electrical signals from transducer elements in a first plurality of
the columns in the array to the first connector region distal
portion of the first structure forming the first wiring pattern;
provide electrical signals from transducer elements in a second
plurality of the columns in the array to the second connector
region distal portion of the first structure forming the second
wiring pattern; and provide electrical signals from transducer
elements in a third plurality of the columns in the array to the
second of the structures forming the third wiring pattern.
6. The system of claim 5 wherein the second of the structures is
configured to: receive electrical signals from the transducer
elements in the third plurality of columns; provide electrical
signals from the transducer elements in one or more first columns
in the third plurality of columns to at least the first and second
distal portions of the second structure; and provide electrical
signals from the transducer elements in one or more second columns
in the third plurality of columns to a third of the structures.
7. The system of claim 1 wherein a first of the structures is
positioned closest to the array relative to a second of the
structures and is configured to: receive electrical signals from
transducer elements in all of the columns in the array; provide
electrical signals from transducer elements in a first plurality of
the columns to the distal portion of the connector region of the
first structure; and provide electrical signals from transducer
elements in a second plurality of the columns to the second of the
structures.
8. The system of claim 7 wherein the second of the structures is
configured to: receive electrical signals from transducer elements
in the second plurality of columns; provide electrical signals from
transducer elements in one or more first columns of the third
plurality of columns to the distal portion of the connector region
of second structure; and provide electrical signals from transducer
elements in one or more second columns in the third plurality of
columns to a third of the structures.
9. The system of claim 1 further including a system console housing
beam forming circuitry, wherein the array of transducer elements
and the plurality of circuit structures are housed in a probe unit
which further includes: a probe electronics unit; a circuit board
providing electrical connection between one of the circuit
structures and the probe electronics unit; and a wiring cable
providing electrical connections between the circuit board and an
electronic component in a remote system console.
10. The system of claim 1 further including a system console
housing beam forming circuitry, wherein the array of transducer
elements and the plurality of circuit structures are housed in a
probe unit which further includes: a plurality of probe electronics
units each electrically coupled to receive signals through a
circuit structure; a wiring cable providing electrical connections
between the probe electronics units and one or more electronic
components in the system console.
11. The system of claim 1 wherein the circuit structures are formed
on flexible circuit boards.
12. The system of claim 1 further including a circuit board
comprising electronics coupled to one or more of the circuit
structures to switch a transducer element between transmit and
receive modes, and provide signal processing and control
functions.
13. The system of claim 1 wherein the major surfaces of the circuit
structures form a laminate structure with adhesive between adjacent
ones of the major surfaces.
14. The system of claim 1 wherein the array of transducer elements
includes a common ground electrode, matching layers, piezoelectric
material, signal electrodes, and a dematching layer.
15. An ultrasonic probe handle comprising: a plurality of flexible
circuits each including first region and one or more connector
regions extending away from each first region, with first regions
of different circuits laminated to one another, each first region
including a plurality of through vias in different first regions
connected to provide electrical interconnection among the flexible
circuits; an array of transducer elements arranged in rows and
columns, each having an electrical connection to at least one of
the flexible circuits, wherein the array of transducer elements is
formed along a first plane and each of the flexible circuits is
formed along a plane parallel with the first plane, wherein two or
more rows and/or two or more columns of said array are electrically
connected to the flexible circuits by at least one of a first
wiring pattern and a second wiring pattern; a circuit board
connected to receive signals from one or more of the transducer
elements through electrical traces formed on one or more of the
flexible circuits; a console housing beam forming circuitry; and a
cable providing electrical connections between the circuit board
and the beam forming circuitry in the system console.
16. The system of claim 14 wherein the circuit board is directly
connected to one of the flexible circuits.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to ultrasonic imaging and, more
particularly, to structures and methods forming electrical
assemblies for acoustic sensors.
2. Background Art
In many ultrasound imaging systems, transducer element signals are
generated in a hand-held probe unit and sent to a system console
through a multi-channel cable system. In some of these systems a
probe may utilize a relatively small array of 128 or 256 transducer
elements with each element connected to the console via the cable
system. Real time 3D ultrasound imaging systems may use larger 2D
arrays of transducers. There are applications in which it is
desirable for large ultrasound arrays to contain thousands or tens
of thousands of transducer elements. With such a large number of
elements, it becomes difficult to route individual connections
between elements in a hand-held probe unit and electronics in the
system console.
In medical imaging applications, this problem has been addressed,
in part, by placing a limited portion of the processing circuitry
in the probe unit instead of in the console. Some designs form the
large array of transducer elements in subarrays, each perhaps
containing 10 to 40 elements, and each subarray has a dedicated
circuit unit providing part of the beamforming function. Each
subarray circuit unit can transfer the signals from all of the
transducer elements in the subarray to a single channel or wire,
e.g., by analog beam formation, so that the signals for all of the
elements in the subarray can be transferred via a single cable lead
to the processing circuitry in the console. In this way thousands
of signals can be carried on a more limited number of lines,
resulting in a manageable cable size.
With continued increases in the size of transducer arrays in an
ultrasound system, it is desirable to place even more processing
electronics in the assembly housing. However, in medical
applications requiring relatively small, light-weight hand-held
probe units, it becomes more of a challenge to provide systems with
higher resolution capability while meeting size and weight
constraints.
Movement of more circuit functions into a hand-held probe unit can
reduce the wire count at the interface between the probe unit and
the cable assembly. This requires an extensive number of additional
connections and routings among transducer elements and circuit
elements which may be placed on multiple circuit boards. With the
transducer array formed along a major plane, a large number of
flexible circuit boards are each positioned with a major surface
thereof in an orthogonal orientation relative to the major plane
along which the transducer array is formed. In such a
configuration, a transducer array having, for example, 64 rows of
elements, can require connection with 64 individual flex circuits.
Additional electronic components providing circuit functions such
as pulse generation and beamforming may be connected to each of the
individual flex circuits, resulting in a relatively large and
complex assembly. Thus while increasing the sizes of image arrays,
e.g., for purposes of increasing image resolution or field, there
is, simultaneously, a need to further reduce the size, complexity
and number of components in the electrical connection
structure.
BRIEF DESCRIPTION
In accord with one embodiment of the invention, an ultrasonic
imaging system includes an array of transducer elements and a
plurality of circuit structures. The transducer elements are
arranged in rows and columns along a first plane for transmitting
and receiving signals. The circuit structures each include a major
surface and a connector region extending away from the major
surface. The major surfaces are positioned in a co-planar
orientation with respect to one another to provide a sequence of
the structures in a stack-like formation. Electrical connections
are formed between adjacent circuit structures in the sequence.
Along each circuit structure a first wiring pattern extends from
each major surface to a distal portion of the connector region. The
plurality of circuit structures is configured to provide a second
wiring pattern extending from one or more of the first wiring
patterns to multiple of the transducer elements.
In another embodiment of the invention, an ultrasonic probe
includes a plurality of flexible circuits each including a first
region and one or more connector regions extending away from each
first region. First regions of different circuits are laminated to
one another. Each first region includes a plurality of through
vias. Through vias in different first regions are connected to
provide electrical interconnection among the flexible circuits.
Transducer elements in an array each have an electrical connection
to at least one of the flexible circuits. A circuit board is
connected to receive signals from one or more of the transducer
elements through electrical traces formed on one or more of the
flexible circuits. A cable provides electrical connections between
the circuit board and beam forming circuitry in an associated
system console.
A method is also provided for fabricating a flexible multilayer
interconnection assembly for an ultrasonic probe. In one
embodiment, a plurality of flexible circuits are provided with
through-vias formed therein and electrical traces formed thereon.
Portions of the circuits are bonded together and electrical
connections between the bonded portions are formed. Each circuit
further includes at least one non-bonded portion extending away
from the bonded portion. An array of transducer elements is
provided along a first plane. The array of transducer elements is
attached to the circuits so that the circuits are oriented in
planes parallel with the first plane. Electrical traces are formed
along non-bonded portions of the flexible circuits and some of the
electrical traces in individual ones of the flexible circuits are
connected to a printed circuit board for processing signals
received by an element in the array.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be more clearly understood from the following
description wherein an embodiment is illustrated, by way of example
only, with reference to the accompanying drawings, in which:
FIG. 1 illustrates a perspective view of a multilayer flex
assembly;
FIG. 2 illustrates a partial schematic cross-sectional view of the
multilayer flex assembly of FIG. 1;
FIG. 3 illustrates a partial schematic plan view of a flex in the
assembly of FIG. 1;
FIG. 4 illustrates a partial schematic plan view of another flex in
the assembly of FIG. 1;
FIG. 5 illustrates an exemplary imaging system incorporating an
embodiment of the invention;
FIG. 6 is a cross-sectional view of a probe handle shown in FIG. 5;
and
FIG. 7 is a partial schematic cross-sectional view illustrating
connection between a flex and a printed circuit board.
Like reference numbers are used throughout the figures to indicate
like features. Individual features in the figures may not be drawn
to scale.
DETAILED DESCRIPTION OF THE INVENTION
In accordance with embodiments of the present invention, systems
comprising interconnection assemblies and methods of forming
interconnection assemblies are described herein. In the following
detailed description, numerous specific details are set forth in
order to provide a complete understanding of a context in which the
present invention may be practiced. However, those skilled in the
art will understand that embodiments of the present invention may
be practices without these specific details and the invention is
not limited to the disclosed embodiments.
Referring now to the drawings, FIG. 1 provides a perspective view
of a portion of a transducer circuit assembly 100 including a
multilayer flexible circuit assembly 1 and a transducer array 2 in
an ultrasonic imaging system 200. The array 2, comprising a large
number of transducer elements 50, such as shown in the cross
sectional view of FIG. 2, is formed about a plane P1, with the
elements 50 arranged in rows x.sub.r and columns y.sub.c. Although
an upper surface of the array 2 is illustrated as co-planar with
the plane P1, the array 2 may be curvilinear in shape about the
plane P1. Rows xr of elements 50 extend along a first direction
parallel with the plane P1, herein referred to as the x direction,
and columns y.sub.c extend along a second direction parallel the
plane P1 and orthogonal to the x direction. For purposes of
illustrating features of example embodiments certain planes and
features, including the plane P1, are referred to as having a
horizontal orientation while other planes and features having an
orthogonal orientation relative to a horizontal feature are
described as having a vertical orientation.
The flexible circuit assembly 1 comprises a large number of
flexible circuit boards, herein referred as "flexes", although, for
simplicity of illustration, a sequence of only four flexes is shown
in FIG. 1. A first flex 10 includes a series of first flex bond
pads 11; a second flex 20 includes series of second flex bond pads
21; a third flex 30 includes a series of third flex bond pads 31;
and a fourth flex 40 includes a series of fourth flex bond pads 41.
All of the flexes are laminated to one another along a central
major surface region 1a which is semi-rigid and positioned along
the plane P1. First and second non-laminated regions 1b and 1b',
herein referred to as connector regions, each extend away from the
region 1a. Each of the connector regions 1b and 1b' includes a
distal portion 1c and 1c', respectively. The distal portions 1c and
1c' on each flex extend in different directions D1 and D2,
respectively, parallel with the x direction and outward from the
central major surface region 1a. Each series of bond pads 11, 21,
31 and 41 is formed along edges of pairs of distal portions in one
of the flexes. For example, the flex 10 includes bond pads 11 on a
first distal portion 1c in the first connector region 1b and a bond
pads 11 on a second distal portion 1c' in the second connector
region 1b'. The bond pads in the distal portion 1c' are illustrated
in phantom lines as they are formed on a lower surface of a flex.
Although not shown in FIG. 1, each bond pad is connected to the
central major surface region by a conductive trace such as shown in
FIGS. 2, 3, and 4. Although not illustrated, the second connector
regions 1b and 1b' may extend away from the laminated surface
region 1a in other directions, e.g., the y direction.
In still other embodiments, more than two connector regions may be
formed such that non-laminated regions extend in all directions
from each semi-rigid laminated surface region 1a. With the major
surface regions 1a of the flexes each having a horizontal
orientation parallel to the plane P1, a series of substantially
vertical electrical connection paths extends through the laminated
major surface regions 1a to route signals between each of the
transducer elements 50 and a bond pad on one of the flexes, such as
a pad in the series of first flex bond pads 11. Although not
illustrated in FIG. 1, bond pads along different edges of a flex
are connectable to printed circuit boards (PCB's) such as shown in
FIGS. 6 and 7. Probe electronic components mounted on PCB's (as
described with reference to FIGS. 5 and 6) provide pulse generation
and beamforming functions in association with related elements 50
of the transducer array 2. In other embodiments each of the series
of flex bond pads 11, 21, 31, and 41 may be formed on an upper
surface or both upper and lower surfaces of a flex.
FIG. 2 is a partial cross-sectional view of the multilayer flex
assembly 100 of the ultrasound imaging system 200 having flex bond
pads formed on the lower surfaces of the flexes, again illustrating
four exemplary flexes 10, 20, 30 and 40 in a larger series of
flexes. The view of FIG. 2 is taken along one of the rows x.sub.r
of transducer elements 50 to illustrate an exemplary connection
configuration between transducer elements 50 and electrical traces
on the flexes 10, 20, 30, and 40.
The transducer array 2 is attached to the circuit assembly 1 with
an adhesive 70. To effect electrical conduction between the circuit
assembly 1 and the transducer array 2, the adhesive must be of the
anisotropically conductive type or may be a non-conductive adhesive
applied and then subjected to heat and pressure so that the
adhesive is displaced as electrical surfaces formed of noble metal
such as gold come into contact with one another. Alternately,
electrical connection between the circuit assembly 1 and the
transducer array 2 may be had with solder balls or "chip on
flex".
The transducer elements 50 each having an upper surface 51 and a
lower surface 52 include a first matching layer 53 along the upper
surface 51, a second matching layer 54 adjoining the first matching
layer 53, a front ground electrode 55 positioned between the
matching layer 54 and a piezoelectric material layer 56, a rear or
signal electrode 57 positioned between the layer 56 and an
electrically conductive dematching layer 58. The signal electrode
57 may be formed by depositing metal on the piezoelectric material
layer 56 before laminating the piezoelectric material layer 56 to
the dematching layer 58. Spacings or kerfs are formed to
electrically isolate the piezoelectric elements 50 in adjacent rows
and columns from one another. For example, the kerfs 61 may be
formed in vertical planes relative to the horizontal plane P1 by
sawing through the layers 56, 57, and 58. Subsequently, the
electrode 55 is formed as a continuous conductive layer over the
elements 50 to provide a common ground. The electrode 55 may be a
thin metal layer (e.g., 0.25-4 microns) formed on the second
matching layer 54 by an electroplating technique and laminated to
the piezoelectric layer 56. The first matching layer 53 may be
laminated to the second matching layer 54 so that both layers 53
and 54 are sawed along the same vertical planes as the
piezoelectric layer is sawed, thereby forming kerfs 62 vertically
aligned with the kerfs 61. The sawing of the matching layer 54
stops short of the ground metallization 55. In this way the
transducer elements 50 are acoustically separated from one another,
but electrically connected via the ground metallization.
The multilayer flex circuit assembly 1 is formed by laminating the
central major surface regions 1a of adjoining flexes, e.g., the
flexes 10, 20, 30, and 40 to one another in a coplanar orientation
with non-conductive adhesive sheets 80 cut to approximately the
length and width dimensions (along the x and y directions) of the
major surface regions 1a. Each sheet (e.g., 80a, 80b, 80c) is
placed between two adjacent flexes with mating contact pads of
adjacent flexes aligned to one another. Each contact pad has a
contact surface formed of a noble metal such as gold. Thicknesses
of the adhesive sheets 80 are generally in the range of 0.010
mm-0.100 mm, sufficient for making electrical contacts without
damaging the mating contact pad pairs. The dimensions of the
adhesive sheets 80 along the directions of the plane P1 are the
same as or slightly smaller than those of the transducer array. The
mating flex contact pads on individual flex circuits become
electrically connected to one another when heat and pressure are
applied in the vertical direction along the regions 1a as excess
epoxy is squeezed from these areas. This produces a sequence of
flexes in a stack-like formation with electrical connections
between adjacent flexes in the sequence. See U.S. Ser. No.
11,560,867 titled "Electronic System With Lead Free
Interconnections and Method of Fabrication", filed Nov. 17, 2006,
assigned to the assignee of the present invention and incorporated
herein by reference.
The first flex 10 having an upper surface 12 and a lower surface
13, includes four upper contact pads 14 (herein referred to as
first flex upper contact pads 14), four through-flex conductive
vias 15 formed in the major surface region 1a (herein referred to
as first flex vias 15), four electrical traces 16 formed on the
lower surface 13 (herein referred to as first flex traces 16), and
four first flex bond pads 11. Two of the four bond pads 11 are
formed in each of the distal regions 1c and 1c'. Each first flex
trace 16 connects a first flex via 15 and a corresponding one of
the first flex bond pads 11. The second flex 20 having an upper
surface 22 and a lower surface 23, includes eight upper contact
pads 24 (herein referred to as second flex upper contact pads 24),
eight through-flex conductive vias 25 (herein referred to as second
flex vias 25), four electrical traces 26 formed on the lower
surface 23 (herein referred to as second flex traces 26), four
second flex bond pads 21 (two of the bond pads 21 formed in each
distal region 1c and 1c'), and four lower contact pads 27, herein
referred as second flex lower contact pads 27. Each second flex
trace 26 connects a second flex via 25 and a corresponding second
flex bond pad 21.
The third flex 30 having an upper surface 32 and a lower surface
33, includes twelve upper contact pads 34 (herein referred to as
third flex upper contact pads 34), twelve through-flex conductive
vias 35 (herein referred to as third flex vias 35), four electrical
traces 36 formed on the lower surface 33 (herein referred to as
third flex traces 36), four third flex bond pads 31 (with two of
the bond pads 31 formed in each distal region 1c and 1c'), and
eight lower contact pads 37, herein referred to as third flex lower
contact pads 37. Each third flex trace 36 connects a third flex via
35 and a corresponding third flex bond pad 31. The fourth flex 40
having an upper surface 42 and a lower surface 43, includes sixteen
upper contact pads 44 (herein referred as fourth flex upper contact
pads 44), sixteen through-flex vias 45 (herein referred as fourth
flex vias 45), four electrical traces 46 formed on the lower
surface 43 (herein referred as fourth flex traces 46), four fourth
flex bond pads 41 (with two of the bond pads 41 formed in each
distal region 1c and 1c'), and twelve fourth flex lower contact
pads 47. Each fourth flex trace 46 connects a fourth flex via 45
and a corresponding fourth flex bond pad 41.
The adhesive layer 80a provides an adhesive bond between the first
flex 10 and the second flex 20. The adhesive layer 80b provides an
adhesive bond between the second flex 20 and the third flex 30. The
adhesive layer 80c provides an adhesive bond between the third flex
30 and the fourth flex 40. In other embodiments, electrical
contacts between flexes may be formed using anisotropically
conductive adhesives with heat and compression, soldering, bumping,
or other common methods.
Still referring to FIG. 2, each transducer element in each row
x.sub.r is connected to a fourth flex via 45 through a layer 59 in
FIG. 2 does not exist. Instead, dematching layer 58 is bonded
directly onto the top flex circuit 40 to make connection to the
bond pads on the top of layer 40 and the upper fourth flex contact
pads 44. The two flex vias 45 connected to the elements 50 in the
two columns y.sub.c closest to the first distal portion 1c and the
two flex vias 45 connected to the elements 50 in the two columns
y.sub.c closest to the second distal portion 1c' are connected
through fourth flex traces 46 to fourth flex bond pads 41 formed
along the lower surface 43 of the fourth flex 40 in the distal
region 1c. With respect to four columns of elements 50, associated
columns of fourth flex vias 45 and associated fourth flex traces 46
effect connection of two columns of elements 50 to the first distal
portion 1c and effect connection of two columns of elements 50 to
the second distal portion 1c', forming a first wiring pattern.
Other columns y.sub.c of fourth flex vias 45 (i.e., other than
those contacting fourth flex bond pads 41) are connected through
the fourth flex lower contact pads 47 to the third flex upper
contact pads 34. The third flex upper contact pads 34 provide
electrical connections between those of the fourth flex vias 45 not
connected to portions 1c and 1c' through the traces 41 and the
third flex vias 35 of the flex 30, forming a second wiring
pattern.
With reference to the flex 30, the third flex vias 35, connected to
the elements 50 in the two columns y.sub.c closest to the first
distal portion 1c, are connected through third flex traces 36 to
third flex bond pads 31 formed along the lower surface 33 on the
distal portion 1c of the flex 30. Similarly, the third flex vias
35, connected to the elements 50 in the two columns y.sub.c closest
to the second distal portion 1c' of the flex 30 are connected
through third flex traces 36 to third flex bond pads 31 formed
along the lower surface 33 on the second distal portion 1c' of the
flex 30. With respect to four columns of elements 50, associated
columns of third flex vias 35 and associated third flex traces 36
effect connection of two columns of elements 50 to bond pads 31 in
the first distal portion 1c of the flex 30 and effect connection of
two columns of elements 50 to bond pads 31 in the second distal
portion 1c' of the flex 30. The second flex upper contact pads 24
formed on the upper surface 22 of the flex 20 provide electrical
connections for those of the third flex vias 35 not connected to
bond pads 31 on the flex 30 through the traces 36. These
connections are made through third flex lower contact pads 37,
second flex upper contact pads 24 and second flex vias 25 of the
flex 20 to the second flex bond pads 21 and the first flex bond
pads 11.
With reference to the flex 20, the second flex vias 25, connected
to the elements 50 in the two columns y.sub.c closest to the first
distal portion 1c, are connected through second flex traces 26 to
second flex bond pads 21 formed along the lower surface 23 on the
distal portion 1c of the flex 20. The second flex vias 25,
connected to the elements 50 in the two columns y.sub.c closest to
the second distal portion 1c' of the flex 20 are similarly
connected through second flex traces 26 to second flex bond pads 21
on the second distal portion 1c' of the flex 20. With respect to
four columns of elements 50, associated columns of second flex vias
25 and associated second flex traces 26 effect connection of two
columns of elements 50 to bond pads 21 in the first distal portion
1c of the flex 20 and effect connection of two columns of elements
50 to bond pads 21 in the second distal portion 1c' of the flex 20.
The first flex upper contact pads 14 provide electrical connections
for those of the second flex vias 25 not connected to portions 1c
and 1c' of the flex 20 through the traces 26. These connections are
made through the second flex lower contact pads 27 and the first
flex vias 15 of the flex 10 to the first flex bond pads 11.
With reference to the flex 10, the first flex vias 15, connected to
the elements 50 in the two columns y.sub.c closest to the first
distal portion 1c, are connected through first flex traces 16 to
first flex bond pads 11 formed along the upper surface 12 on the
distal portion 1c of the flex 10. Similarly, the first flex vias
15, connected to the elements 50 in the two columns y.sub.c closest
to the second distal portion 1c', are connected through first flex
traces 16 to first flex bond pads 11 formed along the lower surface
13 on the second distal portion 1c' of the flex 10. With respect to
four columns of elements 50, associated columns of first flex vias
15 and associated first flex traces 16 effect connection of two
columns of elements 50 to bond pads 11 in the first distal portion
1c of the flex 10 and effect connection of two columns of elements
50 to bond pads 11 in the second distal portion 1c' of the flex
10.
Understanding that that the assembly 100 contains a larger number
of flexes than the illustrated four flexes, the flex 10 may include
additional first flex upper contact pads (not shown), to provide
electrical connections for additional flex vias 15 (not
illustrated) which are not connected to bond pads 11. These
connections are made through additional contact pads (not shown)
formed on the lower surface 13 of the flex 10 and the flex vias of
another flex (not shown) positioned in the sequence containing the
flexes 40, 30, 20 and 10, and following the flex 10. The
above-described interconnect configuration continues with
additional flexes in the sequence in order to route connections in
all of the columns y.sub.c to bond pads along distal portions 1c
and 1c' on other flexes in the sequence for further connection to
other circuit components such as printed circuit boards.
Stacked vias formed in each major surface region 1a and associated
electrical traces extending to distal portions in the same flex
provide electrical connections between individual transducer
elements 50 and a corresponding bond pad in the flex. Electrical
connections between individual transducer elements 50 and a
corresponding fourth flex bond pad 41 are provided by the fourth
flex via 45 and fourth flex traces 46. Electrical connections
between individual transducer elements 50 and a corresponding third
flex bond pad 31 are provided by vertical alignment and
interconnection between third flex vias 35, fourth flex vias 45,
and third flex traces 36. Electrical connections between individual
transducer elements 50 and a corresponding second flex bond pad 21
are provided by vertical alignment and interconnection between
second flex vias 25, third flex vias 35, fourth flex vias 45, and
second flex traces 26. Electrical connections between individual
transducer elements 50 and a corresponding first flex bond pad 11
are provided by vertical alignment and interconnection between
first flex vias 15, the second flex vias 25, the third flex vias
35, the fourth flex via 45, and first flex traces 16.
In FIGS. 3 and 4 electrical connections between individual flex
vias and corresponding bond pads in the first flex 10 and the
second flex 20 are described in plan views. FIG. 3 is a partial
plan view of the first flex 10 taken along a second plane P2
parallel to the first plane P1 (as shown in FIG. 2), and through
the first flex upper contact pads 14. Components shown in phantom
lines are above or below the plane P2. FIG. 3 illustrates several
flex vias 15 in a first row (along the x.sub.r direction) of such
vias, indicated as 15-11, 15-12, 15-13, 15-14, each connected with
one of the first flex traces 16, indicated as 16-11, 16-12, 16-13,
and 16-14, to effect connection with corresponding bond pads 11,
indicated as 11-11 and 11-12 in the first distal region 1c and
11-13 and 11-14 in the second distal region 12c'. By way of
example, the connection between the upper first flex contact pad
14-11 and the corresponding first flex bond pad 11-11 comprises the
pad 14-11 connected to the first flex via 15-11, connected to a
first flex trace 16-11, connected to the first flex bond pad
11-11.
FIG. 4 is a partial plan view of the second flex 20 taken along the
plane P3 (shown in FIG. 2), which is parallel with the planes P1
and P2, and through the second flex upper contact pads 24.
Components shown in phantom lines are above or below the plane P3.
In FIG. 4 the second flex vias 25-11 and 25-12 with lower second
flex contact pads 24-11, 24-12 are connected to the corresponding
second flex bond pads 21-11 and 21-12 in the first distal region 1b
by the second flex traces 26-11 and 26-12, respectively. The second
flex vias 25-17 and 25-18 are connected to the corresponding second
flex bond pads 21-17 and 21-18 in the second distal region 1b' by
the first flex traces 26-17 and 26-18, respectively. By way of
further illustration, the connection between an upper second flex
contact pad 24-11 and the corresponding second flex bond pad 21-11
comprises the pad 24-11 connected to the first flex via 25-11,
connected to the second flex trace 26-11, connected to the second
flex bond pad 21-11. The four second flex vias 25-13, 25-14, 25-15,
and 25-16 are connected to the corresponding lower second flex
contact pads 24-13, 24-14, 24-14, 24-15, 24-16 which are connected
to the upper first flex contact pads 14-11, 14-12, 14-13, and 14-14
in FIG. 3 for connection to the first flex bond pads 11-11, 11-12,
11-13, and 11-14 via the first flex traces 16-11, 16-12, 16-13, and
16-14 as already described with regard to FIG. 3.
FIG. 5 is a simplified block diagram of the ultrasonic imaging
system 200 including a system console 210, connected to a probe
unit 220 by a cable bundle 250, and a display 260. The probe unit
220 includes the multilayer flex transducer assembly 100,
configured in accord with the example shown in FIGS. 1-4. A partial
view of the assembly 100 is shown, having a stack 222 of flexes
224, such as the flexes 10, 20, 30 and 40 shown in FIG. 2 and an
array 2 of transducer elements 50, such as illustrated in FIG. 2.
One exemplary flex 224 and four columns of transducer elements 50
are shown in this simplified schematic view, which is taken along
the direction of a row x.sub.r. It is to be understood that, for
the embodiment of FIGS. 1-4, the stack 222 will include a large
number of flexes 224, each connected to a number of columns y.sub.c
of elements 50. Each flex 224 transfers input and output signals
between elements 50 in several columns y.sub.c (see FIGS. 2-4) and
multiple ones of the probe electronics units 235. Each unit 235
provides signal processing and control functions to a column
y.sub.c of transducer elements 50 and includes a
transmitter/receiver switch 236, transmitter circuitry 237, and
receiver circuitry 238. Signals from the exemplary flex 224
connected to the first two transducer columns y.sub.c are
transferred to two probe electronics units 235 mounted on a first
printed circuit board 230-1 and signals from the exemplary flex 224
connected to the last two columns y.sub.c are transferred to two
probe electronics units mounted on a second printed circuit board
230-2. Signal processing performed in a probe electronics unit 235,
referred to as probe beamforming, can reduce the number of cables
required in the cable bundle 250 when a multiplexing/demultiplexing
algorithm is employed in the probe beamforming circuitry.
The system console 210 includes a system controller 212, main
beamforming circuitry 214, an image processor 216, and a scan
converter 218. The system controller 212 is coupled to the main
beamformer 214, the image processor 216, and a plurality of
transmitters 237 of the probe electronics 235 on the PCB 230 to
provide necessary timing signals to each of the various devices. In
operation of the system 200, each transmitter 237 provides
electronic transmit signals to a transducer element 50 which
converts the electrical signals to ultrasonic pressure waves herein
illustrated by ultrasound lines 242. A portion of the transmitted
energy may return to the array as reflections 244 after interacting
at boundaries of a feature 246 on an object 240 having an abrupt
transition in acoustic impedance.
FIG. 6 further illustrates an exemplary application of the
embodiment shown in FIGS. 1-5. A probe unit 310 of the ultrasound
imaging system 200 is shown containing the multilayer flex
transducer assembly 100 having a plurality of flexes 320, a
plurality of Printed Circuit Boards (PCBs) 330 each containing a
plurality of probe electronics units 340, Flexible connectors 361
carry signals between the PCBs 330 and a cable connector 355. The
connector 355 receives a mating connector 356 in which individual
wires of a cable bundle 250 terminate to effect connection to
circuitry (such as the main beamformer 214 illustrated in FIG. 5)
in the system console 210.
The exemplary flex circuit assembly 1 includes a major surface
region 1a and a first connector region 1b and a second connector
region 1b'. The connector regions 1b and 1b' of individual flexes
320 in the circuit assembly 1 are each connected to a corresponding
Printed Circuit Board (PCB) 330. In other embodiments, the flexes
320 may be attached to semi-rigid Flexible Circuit Boards (FCBs).
The connector regions 1b and 1b' may be joined with the PCBs 330 by
a clamp 325 as illustrated in FIG. 6. The electronic components 340
can be mounted directly onto the flex circuits with the circuit
routing made to the individual electronic components via flex
traces.
FIG. 7 illustrates another wiring configuration for the probe unit
310. A flex 320 and a PCB 330 are bonded together with an
anisotropically conducting film (ACF) 370 to provide a multilayer
flex transducer assembly having a plurality of flexes 320 and a
plurality of Printed Circuit Boards (PCBs) 330. The flex 320,
having an upper surface 321 and a lower surface 322, includes a
plurality of flex bond pads 323 formed along the lower surface 322.
The PCB 330 includes an upper dielectric layer 335 formed over an
intralevel dielectric layer 337 formed over a lower dielectric
layer 338. The upper dielectric layer includes an upper surface 331
and a lower surface 332, and comprises a plurality of PCB contact
pads 333 formed on the upper surface 331. Upper level vias 334 are
formed in the upper level dielectric layer 335. Underlying inner
conductors 336 are formed in the intra-level dielectric layer 337.
Electrical conductors 372 are formed between the flex bond pads 323
and the PCB contact pads 333 when heat and pressure are applied to
the anisotropically conducting film 370. In other embodiments,
electrical contacts between the flexes and the PCBs may be formed
by soldering, or with other common methods.
A structure has been illustrated for connecting electronic
components to an array of transducer elements and a low cost
process has been illustrated for producing the structure. In the
past, connection of an array of transducer elements has provided
signals to and from one entire row or column of the array through a
single flex. Flex costs increase as the trace pitch decreases, and
overall cost per flex increases as the number of elements connected
to one flex increases. However, a significant savings in overall
cost can be realized based on a net reduction in the number of
flexes required to process signals associated with the entire
array.
While various embodiments of the invention have been illustrated
and described, the invention is not so limited. Numerous
modifications, variations, substitutions and equivalents will occur
to those skilled in the art without departing from the spirit and
scope of the present invention as described in the claims.
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